A resin molding product having a fine pattern is useful such as an optical element (a micro lens array, an optical waveguide, an optical switching, a Fresnel zone plate, a binary optical element, a blaze optical element, a photonics crystal, or the like), an anti-reflection filter, a biochip, a microreactor chip, a recording medium, a display material, a carrier for a catalyst. There has been recently a demand for acquisition of smaller devices as well as finer patterns thereof. As a method for preparing a resin molding product having such a fine structure over its surface, there has been proposed a method in which a pattern of a mold having a fine pattern is transcribed on a resin to produce an imprint product having a fine pattern formed thereon, that is, a so-called nanoimprint method (see, for example, Patent Documents 1 and 2). Furthermore, as a method substituting for a photolithographic method in a process of manufacturing semiconductor, there has been proposed a nanoimprint method in which a resist is coated on a silicone substrate and a mold having a fine pattern formed thereon is pressed to transcribe the fine pattern on the resist (see, for example, Patent Documents 3 and 4).
However, in any of the above-mentioned nanoimprint methods, a step of releasing a mold has suffered from a problem that the mold is not smoothly released and the shape precision of fine patterns in the imprint product is reduced. Thus, in order to smoothly release the mold, an attempt has been made to coat a release agent on a mold surface. In this case, there have been problems that unevenness in the thickness of a release agent layer causes reduction of the pattern precision of a mold, and that the release agent layer becomes thinner due to successive use of the mold, and accordingly, there occurs a need to coat a release agent on the mold again, leading to reduction of the productivity.
In order to solve these problems, there has been proposed a method in which a non-adhesive material having a non-adhesive surface energy of less than about 30 dyn/cm is used as a mold material (Patent Document 5). Examples of the non-adhesive material include fluoropolymers such as a fluorinated ethylene propylene copolymer, a tetrafluoroethylene polymer; fluorinated siloxane polymers; silicones; and the like.
However, the method described in Patent Document 5 includes imprinting a mold or its negative pattern made of a non-adhesive material onto a photocurable or thermosetting thin film formed on a substrate. that is, the method uses a mold or its negative pattern as a lithographic tool. In Patent Document 5, the non-adhesive material is intended to serve mainly as a release agent. Further, a mold using silicone has a low elastic modulus, and it is difficult to imprint a pattern shape precisely.
Furthermore, in Patent Document 6, there is disclosed a method for forming a pattern on a transcription layer, which consists of a step in which a thermoplastic resin containing a fluorine-containing polymer which has 35% by mass or more of a fluorine content, is pressed with a mold having an inverse pattern of a desired pattern, and thereby forming a desired pattern on the transcription layer; and a step in which the mold is released from the transcription layer. It is described that according to this method, the releasability of the transcription layer is excellent and a fine pattern can be formed. Herein, examples of the fluorine-containing polymer include polytetrafluoroethylene, a 1,1,1-trifluoro-2-trifluoromethylpenten-2-ol copolymer, a perfluorocyclic ether polymer (trade name CYTOP (registered trademark)), a copolymer of chlorotrifluoroethylene and vinyl ether (trade name LUMIFLON (registered trademark)), and the like.
However, when the fluorine content of these polymers is 60% by mass or less, their dimensional accuracy in terms of the depth, width and interval of convex structures is low and dimensional difference is large, because the elastic modulus is rapidly decreased at a temperature above the glass transition temperature, and after the polymer is subjected to press molding, when cooling rapidly, the shrinkage ratio is increased due to the decreased elastic modulus. In addition, even if fluorine content is 60% by mass or more, the fluorine resins such as polytetrafluoroethylene which exhibit a high melting point temperature (Tm), since it is necessary to set the molding temperature markedly higher, provide significant differences in the dimensions between the convex structure mold and the imprint product because of increase in the differences between the elastic modulus and shrinkage ratio during the process of heating and cooling. Furthermore, the fluorine resins must be pressed at temperature of 300° C. or higher which associate with a high possibility of decomposition of the fluorine resins when heated at the temperature of 260° C. higher to generate hydrogen fluoride gas and therefore, there occur problems such as corrosion of molds and peripheral devices, environmental pollution.
The imprint methods which comprise molding by heat press as suggested as described above, are required to uniformly put high pressure on a large area in order to obtain an imprint product with a large area, and thus a large-sized heat press molding machine is necessitated. Thus, there is a large problem in manufacturing an imprint product with a large area because of limitations on the area of the imprint product that can be industrially processed.